Testing
Amazon Deequ is an open-source data quality library built on Apache Spark, developed and used internally at Amazon to validate the quality of datasets at petabyte scale. Unlike SQL-based tools that work on a single database, Deequ runs as part of your Spark job — making it ideal for validating data
Testing
Datafold is a data reliability platform that specializes in data diffing — comparing two versions of a dataset to detect changes introduced by a pipeline update. When you change a dbt model, a SQL transformation, or an ETL job, Datafold shows you exactly which rows changed, which columns were affected, and
Testing
Monte Carlo is a data observability platform that monitors data pipelines using ML-powered anomaly detection rather than manually defined thresholds. Instead of writing checks for every column, Monte Carlo learns your data's normal behavior and alerts when something changes unexpectedly. This guide covers how to test with Monte
Testing
Data contracts are the data engineering equivalent of API contracts — a formal agreement between data producers and consumers about the structure, semantics, and quality of data. In data mesh architectures, where multiple teams own data products, contracts prevent the silent schema changes, missing fields, and format shifts that cause downstream
Testing
WebAuthn (Web Authentication API) enables passwordless authentication using hardware security keys, platform authenticators, and biometrics. Testing WebAuthn flows presents unique challenges: the API requires browser interaction with physical hardware, and the ceremonies (registration and authentication) involve cryptographic operations that normally can't be scripted. Playwright solves this with virtual
Testing
SimpleWebAuthn is the most widely used open-source WebAuthn library for JavaScript servers. Its @simplewebauthn/server package handles the complex cryptographic operations for credential registration and authentication verification, so you don't have to implement CBOR parsing, COSE key validation, or attestation verification yourself. But even with a battle-tested library,
Testing
Passkeys are the consumer-friendly implementation of FIDO2/WebAuthn, introduced by Apple, Google, and Microsoft as a coordinated standard for passwordless authentication. Unlike hardware security keys, passkeys sync across devices via iCloud Keychain, Google Password Manager, and Microsoft's ecosystem — which introduces testing challenges around cross-device scenarios, OS-level dialogs, and
Testing
FIDO2 is the authentication standard that powers WebAuthn and passkeys. It encompasses two layers: WebAuthn (the browser API) and CTAP2 (the Client-to-Authenticator Protocol). Testing FIDO2 authenticators — hardware security keys like YubiKey, software authenticators, and platform authenticators — requires strategies for both the protocol layer and the application layer. This guide covers
Testing
Biometric authentication — Touch ID, Face ID, Windows Hello, fingerprint readers — powers the most seamless login experiences on the web and in mobile apps. It also creates one of the hardest testing challenges: you can't script a fingerprint or a face scan. But biometric auth sits on top of
Testing
Unleash is an open-source feature management platform used by thousands of teams to control feature rollouts without code deploys. But the flexibility that makes Unleash powerful — custom activation strategies, gradual rollouts, user segmentation — also makes testing more complex. This guide covers every layer of Unleash testing from SDK mocks to
Testing
Split.io combines feature flags, experimentation, and observability in a single platform. Its treatment-based model — where flags return named treatments like "on", "off", or custom variant names — requires test strategies that go beyond simple boolean checks. This guide covers Split.io-specific testing patterns from unit tests
Testing
OpenFeature is a CNCF specification that standardizes how applications interact with feature flag systems. Instead of coupling your code to LaunchDarkly, Unleash, or Flagsmith APIs, you code against the OpenFeature API — and swap providers without changing application code. But this abstraction layer introduces new testing requirements. You must test the